Antisolvent dewaxing



Patented May 9, 1933 UNITED STATES PATENT OFFICE JOHN A. ANDERSON, OF CHICAGO, ILLINOIS, ASSIGNOR TO STANDARD OIL COMPANY, OF

CHICAGO, ILLINOIS, A CORPORATION OF INDIANA AN'rIsoLvnNT nnwaxme causes the oil to solidify or to unduly resist flow at low temperatures.

Dewaxing may be accomplished by mixing the oil with a highly fluid diluent, chilling the mixture to solidify the wax and throw it out of solution, mechanically separating the wax from the chilled mixture, and separating the wax-free oil from the diluent by distillation. The effectiveness of this process depends, to a considerable extent, on the nature of the diluent; the diluent should be readily miscible with the oil and should not separate therefrom even at the lowest chilling temperatures; it should be extremely fluid or non-viscous at the chilling temperatures it should tend to throw wax out of solution in a physical form that will facilitate mechanical separation by filtering, centrifuging or settling; it should be chemically inert and it should be relatively inexpensive.- The .object of my invention is to provide such a diluent. c

A further object of my invention is toprovide a diluent which will overcome difiiculties encountered in the use of diluents here-, tofore known. A further object is to provide a diluent which can be successfully used on all types of mineral oils by a slight variation in proportions. A further objectjs to pro vide a means for using an acetone-benzol mixture for dewaxing heavy oils without causing the benzol to freeze out and without causing the heavy oil to separate from the diluent. Other objects will be apparent as the detailed description of my invention pro ceeds.

\ Acetone is an antisolvent for wax. However, the antisolvent ower of acetone is so great that it cannot used by itself as a 1931. Serial No., 529,298.

diluent, but must be blended with a secondary solvent which will prevent the oil from separating out with the wax. Coal tar benzene (benzol is a very good secondary solvent and an effective mixture is 62% benzol and 38% acetone.

This mixture is not satisfactory for dewaxing heavy oils, particularly oils of the Pennslvania type, at low tem eratures because the oil is thrown out of so ution as-well as the wax. If the percentage of benzol is increased, the benzol will crystallizeor freeze out. If the percentage of acetone is increased, the

tendency for the oil to separate out will likewise increase. Mid-Continent lubricating oil of S. A. E. 40 viscosity', or a Pennsylvania lubricating oil of S. A. E. 30 cannot be satisfactorily dewaxed with an acetone benzol, mixture at temperatures of -10 F. Oils in the range of S. A. E. viscosity 50 and 60 are 7 even more difficult to dewax.

I have discovered that the addition of a third ingredient to the acetone benzol diluent will overcome theltendency of the oil to separate 'out and the tendency of the benzol to E crysallize out at dewaxing temperatures.

The new ingredient must have a low freezing point and a high afiiriity for oil, and it must and point 250 F.,a'pproximate boilingrange of diluent mixture). In practicing my invention I prefer to slightly increase the proportion of benzol and to decrease the proportion of acetone, as will be hereinafter set F. of from 70 to 120 seconds-is most efl'ective- 1y dewaxed by the use of a diluent consisting of 32%. acetone, 65%

A Mid-Contment oil having a 210 F. from seconds to 180 seconds requires more naphtha, a; preferred formula bemiscible with acetonea'nd benzol; I prefer I to use naphtha (initial boiling point 'F., 80

benzol, and 3% naphtha.

acetone, 65% benzol and 5% naphtha.

Pennsylvania, oils and oils of similar temperature viscosity coeflicient require still furthey-amounts. of naphtha to maintain a homogeneous mixture at 10 F. Forinstance, a Pennsylvania oil having a viscosity at 210 F. of from 45 to 60 seconds requires 30% acetone, 65% benzol and-5% naphtha. Pennsylvania oil from 60 to 100 seconds at 210? F. requires 27% acetone, 65% benzol and 8% na htha, and 140 seconds (viscosity at 210 F.) ennsylvania oil. requires 25% acetone, 65% benzol and 10% naphtha.

' While I have specifically described my invention as applied to a mixture of acetone and benzol, it is understood that I do not limit myself to the above details. For instance, I may. use methyl formate, methyl carbonate, methyl ethyl ketone, etc. instead of acetone. When using these antisolvents, however, the

proportion ofnaphtha required will varysomewhat from that required when using acetone, depending on their antisolvent power. I

In the diluent, as above described, the function of the naphtha is not merely to reduce theviscosity of the oil, the use of naphtha for this purpose being well known. In the formulas hereinabove set forth the na htha serves an entirely different purpose. vents the separation of hea oils from acetone without freezing out t e benzol or, in other -words, it serves to maintain the chilled diluent in a fluid state. This is robably due to the fact that naphtha is c osely associated chemically with the mineral 011 and at the same time is miscible with the benzol and acetone. The specific solvents hereinabove set forth have been found to give re-.

markably eflicient separation of wax from oil at low chilling temperatures.

bodimentof my invention it is understood that I do n limit myself .to the details thereinset forth except as defined by the following claims I 7 I claim:

'le I hav described a' preferred em ing heavy mineral oils which comprises about 30% acetone, 65%"benzol and 5% naphtha.

6. The method of dewaxing heavy mineral I 7. The method of dewaxing heavy mineral lubricating oil which comprises diluting said oil with a homogeneous solution of.

acetone, benzol and a small amount'of naphtha, chilling said mixture to effect solidifica tion-of the wax, mechanically separating the diluted mixture from solidified wax, and distillingsaid diluent from the dewaxed oil.

In witness whereof I have aflixed my signature.

JOHN A.A NDERSON.

1. An antisolvent dew'axing'mixture for I petroleum oils which comprises about 65% benzol, at least 25% of acetone and enough naphtha to prevent'the separation of oil from diluent when the mixture is chilled to 10 F..

2. An antisolvent diluent for use in dewaxing heavy mineral oils which comprises about 65%benzol', 25 to 32% acetone, and 3 to 10% naphtha.

3.. An antisolvent diluent for use in dewaxing heavy mineral oils which comprises about 25% acetone, 65% benzol and 10% naphtha. 4. An antisolvent diluent for use in de waxing heavy mineral oils which comprises about 32% acetone, 65% benzol and 3% naphtha.

5. An antisolvent diluent for use in dewax- 

